fast trig with binary math.c

// 375 loops per second
// –  Arduino Uno R3 -

// Thanks to FastLED Math library:
//   https://github.com/FastLED/FastLED/wiki/High-performance-math

void sinePixels() {
  uint8_t timeScale = 20;
  long time = millis() * timeScale;
  
  long r, g, b;

  for (uint8_t x = 0; x < 8; x++) {
    for (uint8_t y = 0; y < 5; y++) {

      // x 16 bit normalized
      uint16_t x16 = x * 0x10000/8; // 1/8 16 bit

      // y 8 bit normalized
      uint8_t y8 = y * 0x100/5; // 1/4 8 bit

      r = (sin16(x16 - time) >> 8) + 128;
      r = 255 - abs(y8 - r);
      r = dim8_raw(r);

      g = (sin16(x16 - time * 2) >> 8) + 128;
      g = 255 - abs(y8 - g);
      g = dim8_raw(g);

      b = (sin16(x16 + time * 3) >> 8) + 128;
      b = 255 - abs(y8 - b);
      b = dim8_raw(b);

      strip.setPixelColor(x + y*8, r, g, b);
    }
  }
  strip.show();
}

slow trig and floats.c

// 20 loops per second
// –  Arduino Uno R3 -

void sinePixels() {
  float brightness = .5;
  float timeScale = 3.0;
  float time = (float)millis() / 1000.0;
  
  float r, g, b;

  for (uint8_t x = 0; x < 8; x++) {
    for (uint8_t y = 0; y < 5; y++) {

      r = sin(x - time*timeScale*3.0) * 0.15 + 0.5;
      r = 1.0 - abs((float)y / 4.0 - r);
      r = pow(r, 3);

      g = sin(x + time*timeScale*2.1) * 0.2 + 0.5;
      g = 1.0 - abs((float)y / 4.0 - g);
      g = pow(g, 3);

      b = sin(x - time*timeScale*1.3) * 0.4 + 0.5;
      b = 1.0 - abs((float)y / 4.0 - b);
      b = pow(b, 3);

      setPixelColor(
        x, y,
        r * brightness,
        g * brightness,
        b * brightness
      );
    }
  }
  strip.show();
}

void setPixelColor(uint8_t x, uint8_t y, float r, float g, float b) {
  strip.setPixelColor(x + y*8, (uint8_t)(r*255), (uint8_t)(g*255), (uint8_t)(b*255));
}